Procainamide

In this lesson, we'll go over the medication procainamide and all of its effects, including indications, precautions and contraindications, and adult dosages. And at the end of the lesson, we provide you with a Word about wide complex tachycardias.

Procainamide is effective at slowing the conduction in the atria, ventricles, and the His-Purkinje system by prolonging the P-R and Q-T intervals and the refractory period of the AV node. Procainamide also slows the refractory period within the atria and ventricles and slows the conduction velocity.

Procainamide Indications

Now let's take a look at procainamide indications.

Procainamide is effective for the treatment of supraventricular tachycardia that returns after vagal maneuvers and adenosine are ineffective.

Procainamide is also effective at treating the following:

• Stable wide complex tachycardia of uncertain origin
• Stable monomorphic ventricular tachycardia with normal QT intervals
• Atrial fibrillation with a rapid ventricular rate of response in patients with Wolff Parkinson White syndrome
• Recurrent ventricular fibrillation
• Pulseless ventricular tachycardia

Procainamide Precautions and Contraindications

Also important to note is that digitalis toxicity may complicate an already existing AV conduction depression. Other procainamide contraindications would include:

• 3rd degree heart block
• Preexisting prolongation of the QRS complexes
• Preexisting prolongation of the QT intervals

Adult Dosage of Procainamide

Now let's look at the adult dosage for procainamide.

If you're administering procainamide for recurrent ventricular fibrillation and pulseless V-tach, you should give 20mg per minute via IV infusion up to total max dose of 17mg per kg.

For supraventricular tachycardia, atrial fibrillation, and wide complex tachycardia of uncertain origin, administer procainamide at 20mg per minute via IV infusion up to a total maximum dose of 17mg per kg.

For maintenance doses of procainamide, administer the drug at 1 to 4mg per minute titrated to the desired effect and the patient response.

It's important to note that the use of procainamide should be stopped if any of the following occurs:

• Arrhythmia suppression
• The onset of hypotension
• The QRS complex widens by more than 50 percent of its pretreatment width
• The maximum dose of 17mg per kg is reached

A Word About Wide Complex Tachycardias

Since wide complex tachycardias are one instance in which you may administer procainamide, let's take a broader look at it.

Wide-complex tachycardias are defined as a QRS of 0.12 seconds or more. The most common types of life threatening wide complex tachycardias that are likely to deteriorate to ventricular fibrillation are:

• Monomorphic ventricular tachycardia
• Polymorphic ventricular tachycardia

You should determine if the rhythm is regular or irregular:

1. A regular wide complex tachycardia is presumed to be ventricular tachycardia or supraventricular tachycardia with aberrancy.
2. An irregular wide complex tachycardia can be the following:
   a. Atrial fibrillation with aberrancy
   b. Pre-excited atrial fibrillation, such as atrial fibrillation using an accessory pathway for antegrade conduction
   c. Polymorphic ventricular tachycardia/torsade's de pointes

These are all advanced rhythms requiring expert consultation.

If the rhythm is likely ventricular tachycardia or supraventricular tachycardia in a stable patient, treat the condition based on the algorithm for that rhythm. If the rhythm etiology cannot be determined and is regular in its rate and monomorphic, recent research and evidence suggests that adenosine administered via IV is relatively safe for both treatment and diagnosis.

IV antiarrhythmic drugs may be effective. The American Heart Association recommends procainamide, amiodarone, or sotalol.

In the case of irregular wide-complex tachycardia, management of the condition should be focused on controlling the rapid ventricular rate, the conversion of hemodynamically unstable atrial fibrillation to sinus rhythm, or both. Again, expert consultation is advised.